The goal is to determine if strenuous maternal aerobic exercise induces the prenatal stress syndrome and its sequelae of impaired reproductive behaviors in male offspring. The proposed research will also evaluate for subtle changes in preweaning neurodevelopmental (motor/reflex) behaviors as well as identify any alterations in CNS morphology, specifically pituitary, that may exist. Female rats will be divided into three groups for treadmill exercise plus one control group. Group I will be pre-conditioned for 4 weeks prior to the onset of mating and subsequent pregnancy. This group will continue to run during the entire gestational period at maximal aerobic capacity. Group II will run during the entire pregnancy, but without benefit of pre-conditioning. As it is known that third trimester exposure to restraint stresses are sufficient to induce the prenatal stress syndrome, Group III will run only during the last trimester, also without pre-conditioning. Prior to weaning, the offspring will be examined for alterations in neurodevelopmental behavior tests including surface righting reflex, negative geotaxis reflex suspension, modified open field activity, spatial maze and continuous corridor. A number of 21 day old offspring will be sacrificed, and the pituitaries examined histologically via light microscopy and electron microscopy for alterations in CNS morphology, particularly of the gonadotrophs. Copulatory behavior of 50 day old adult male offspring will be observed and androgen injections (testosterone propionate) given to the non-ejaculators daily for 6 weeks. Presence or lack of androgen-mediated copulatory behavior will be assessed. If it is shown that maternal exercise stress alters the developing neuroendocrine system, then women should be alerted that many of the other causes of stress undertaken during pregnancy may also have delayed effects on the biological functions of their offspring. Identification of a sequence of delayed or altered neurodevelopmental behaviors may permit earlier intervention and disruption of progression.